This invention relates to optical apparatus in general, and more particularly to an improved coarse viewing system for an annular field projection system.
In copending applicaton Ser. No. 339,860 filed Mar. 9, 1973 and assigned to the same assignee as the present invention, an optical projecting and scanning apparatus useful in producing integrated circuits is disclosed. The disclosed apparatus requires alignment between a mask and a semiconductor wafer. Alignment is carried out by an operator who adjusts controls to effect relative motion between the wafer and mask. However, in order for the operator to properly carry out this alignment, he must be able to observe the results of the movement which he causes at the wafer. The aforementioned application discloses two viewing systems for making such alignment.
A fine alignment system which permits simultaneous viewing of two points on the wafer or other object is disclosed in the aforementioned copending applicaton Ser. No. 339,860 and is also disclosed and claimed in application Ser. No. 509,587 of W. H. Newell filed Sept. 26, 1974 now U.S. Pat. No. 3,937,556. However, before such fine alignment can be efficiently carried out, a coarse alignment is required. That coarse alignment apparatus is disclosed and claimed herein.